package com.nxy.cpfsfe.util.zookeeper;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Created by lcq on 2019/9/5.
 */
public class DistributedLock implements Watcher,Lock {
    private static final Logger logger = LoggerFactory.getLogger(DistributedLock.class);
    private ZooKeeper zk;
    private String root = "/locks";//根
    private String lockName;//竞争资源的标志
    private String waitNode;//等待前一个锁
    private String myZnode;//当前锁
    private volatile CountDownLatch latch;//计数器
    private List<Exception> exception = new ArrayList<Exception>();
    private final static String splitStr = "_lock_";
    private final static long defaultWaitTime = 30*1000;

    /**
     * 创建分布式锁,使用前请确认config配置的zookeeper服务可用
     * @param config 127.0.0.1:2181
     * @param lockName 竞争资源标志,lockName中不能包含单词lock
     */
    public DistributedLock(String config, String lockName){
        this.lockName = lockName;
        // 创建一个与服务器的连接
        try {
            config=config.replace("?backup=",",");

            zk = new ZooKeeper(config, 30*1000, this);

            Stat stat = zk.exists(root, false);
            if(stat == null){
                // 创建根节点
                zk.create(root, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);
            }
        } catch (IOException e) {
            exception.add(e);
        } catch (KeeperException e) {
            exception.add(e);
        } catch (InterruptedException e) {
            exception.add(e);
        }
    }

    /**
     * zookeeper节点的监视器
     */
    public void process(WatchedEvent event) {
        if(this.latch != null) {
            this.latch.countDown();
        }
    }

    /*
     * 申请锁的默认时间是 defaultWaitTime ，超时后抛出LockException运行时异常
     */
    public void lock() {
        try {
            if(this.tryLock()){
                logger.debug("Thread " + Thread.currentThread().getId() + " " +myZnode + " get lock true");
                return;
            } else{
                waitForLock(waitNode, defaultWaitTime, TimeUnit.MILLISECONDS, true);//等待锁
            }
        } catch (KeeperException e) {
            throw new LockException(e);
        } catch (InterruptedException e) {
            throw new LockException(e);
        }
    }

    /*
     * 非阻塞方式获取锁
     * 如果存在锁返回false
     * 通过判断返回值判断是否获取锁成功
     */
    public boolean tryLock() {
        logger.debug("zookeeper添加临时锁：[{}]",lockName);
        if(exception.size() > 0){
            throw new LockException(exception.get(0));
        }
        try {
            if(lockName.contains(splitStr))
                throw new LockException("lockName can not contains \\u000B");
            //创建临时子节点
            myZnode = zk.create(root + "/" + lockName + splitStr, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL_SEQUENTIAL);

//            myZnode = zk.create(root + "/" + lockName + splitStr, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL);
            logger.debug(myZnode + " is created ");
            List<String> lockObjNodes = this.getChildrenListSort();
            logger.debug(myZnode + "==" + lockObjNodes.get(0));
            if(myZnode.equals(root+"/"+lockObjNodes.get(0))){
                //如果是最小的节点,则表示取得锁
                return true;
            }
            //如果不是最小的节点，找到比自己小1的节点
            String subMyZnode = myZnode.substring(myZnode.lastIndexOf("/") + 1);
            waitNode = lockObjNodes.get(Collections.binarySearch(lockObjNodes, subMyZnode) - 1);
        } catch (KeeperException e) {
            throw new LockException(e);
        } catch (InterruptedException e) {
            throw new LockException(e);
        }
        return false;
    }

    /*
     * 非阻塞方式获取锁
     * 通过判断返回值判断是否获取锁成功
     */
    public boolean tryLock(long time, TimeUnit unit) {
        try {
            if(this.tryLock()){
                return true;
            }
            return waitForLock(waitNode,time,unit,false);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return false;
    }

    /**
     * @param lower 次小节点
     * @param waitTime 等待时间
     * @param unit 时间单位
     * @param isBreak 超时是否抛出异常
     * @return
     * @throws InterruptedException
     * @throws KeeperException
     */
    private boolean waitForLock(String lower, long waitTime, TimeUnit unit,boolean isBreak) throws InterruptedException, KeeperException {
        long beginTime = System.currentTimeMillis();
        Stat stat = zk.exists(root + "/" + lower,true);
        //判断比自己小一个数的节点是否存在,如果不存在则无需等待锁,同时注册监听
        if(stat != null){
            logger.debug("Thread " + Thread.currentThread().getId() + " waiting for " + root + "/" + lower);
            this.latch = new CountDownLatch(1);
            this.latch.await(waitTime, unit);
            if(this.latch.getCount() == 1){
                this.latch = null;
                if(isBreak){
                    throw new LockException("申请锁资源默认时间是："+defaultWaitTime+"ms,等待锁超时");
                }else{
                    return false;
                }
            }
            this.latch = null;
        }

        //取出所有lockName的锁
        List<String> lockObjNodes = this.getChildrenListSort();
        logger.debug(myZnode + "==" + lockObjNodes.get(0));
        if(myZnode.equals(root+"/"+lockObjNodes.get(0))){
            //如果是最小的节点,则表示取得锁
            return true;
        }else{
            //如果不是最小的节点，找到比自己小1的节点
            String subMyZnode = myZnode.substring(myZnode.lastIndexOf("/") + 1);
            waitNode = lockObjNodes.get(Collections.binarySearch(lockObjNodes, subMyZnode) - 1);
            long endTime = System.currentTimeMillis();
            waitTime = waitTime - (endTime - beginTime) ;
            if(waitTime <= 0) return false;
            return waitForLock(lower, waitTime, unit, false);//等待锁
        }
    }

    /**
     * 取出本次锁的所有子节点（升序）
     * @return
     * @throws LockException
     */
    private List<String> getChildrenListSort() throws KeeperException, InterruptedException{
        //取出所有子节点
        List<String> subNodes = zk.getChildren(root, false);
        //取出所有lockName的锁
        List<String> lockObjNodes = new ArrayList<String>();
        for (String node : subNodes) {
            String _node = node.split(splitStr)[0];
            if(_node.equals(lockName)){
                lockObjNodes.add(node);
            }
        }
        Collections.sort(lockObjNodes);
        return lockObjNodes;
    }

    public void unlock() {
        logger.debug("zookeeper删除临时锁：[{}]",lockName);
        try {
            logger.debug("unlock " + myZnode);
            if(null != myZnode){
                zk.delete(myZnode,-1);
            }
            myZnode = null;
            zk.close();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (KeeperException e) {
            e.printStackTrace();
        }
    }

    public void lockInterruptibly() throws InterruptedException {
        this.lock();
    }

    public Condition newCondition() {
        return null;
    }

    public class LockException extends RuntimeException {
        private static final long serialVersionUID = 1L;
        public LockException(String e){
            super(e);
        }
        public LockException(Exception e){
            super(e);
        }
    }

}


